1. Field of the Invention
This invention relates to the manufacture of a continuous length of coupling element of the known helicoidal-coil type together with a continuous length of core cord received in place therein, for use in slide fasteners. More specifically, the invention is directed to a method of, and means for, feeding the core cord to a coiling station in which a continuous filament of desired material is coiled while receiving the core cord in place within its successive turns or convolutions.
2. Description of the Prior Art
Apparatus for the manufacture of a continuous length of helicoidal-coil type coupling element together with a continuous core cord received in place therein is described and claimed in Japanese Pat. Pub. No. 45-40939, published on Dec. 22, 1970. Further, of this apparatus, means for feeding at a controlled rate the continuous core cord to be received within the continuous coupling element is separately described and claimed in Japanese Pat. Pub. No. 46-1132, published on Jan. 12, 1971.
According to the second mentioned Japanese patent, the continuous core cord travelling from a pay-off bobbin to coiler mechanism is made to pass over a guide roller rotatably mounted on a reciprocating lever. This lever is oscillated in step with the reciprocation of a mandrel holder toward and away from the coiler mechanism so that successive unit lengths of the core cord may be taken away from the pay-off bobbin by the oscillatory motion of the guide roller.
It has been later found that according to this prior art core cord feed mechanism, the successive lengths of the core cord taken away from the pay-off bobbin tend to fluctuate. Another serious disadvantage is that the successive lengths of the core cord are fed into the coiler mechanism in a more or less tensed or extended state. This is objectionable for the following reason.
In stitching helicoidal-coil type coupling elements onto carrier tapes, the stitches are usually passed through the core cord within the coupling elements. Receiving the stitches, the core cord tend to meander and to bulge or swell at intervals. This results in some reduction in the lengths of the core cord. It will therefore be seen that the core cord must be fed into the coiler mechanism at a rate anticipating the above lengthwise reduction on stitching.
The noted prior art core cord feed mechanism is further disadvantageous in that it does not permit ready adjustment of the unit length of the core cord to be fed into the coiler mechanism or to be taken away from the pay-off bobbin. This disadvantage is a direct result of the fact that the reciprocation of the mandrel holder is utilized both for pulling successive lengths of the core cord away from the pay-off bobbin and for feeding them into the coiler mechanism. Each unit length of the core cord to be taken away from the pay-off bobbin must be readjusted when, for example, a change is made from one core cord to another of different material or make. If such readjustment is not effected, the rate at which the new core cord is actually fed into the coiler mechanism may inordinately increase or decrease because of the different degree of frictional resistance to which the core cord is subjected on its way from the pay-off bobbin to the coiler mechanism.